Pulley slips on motor shaft

The motor pulley keeps sliding to the outside. The belt gets pulled toward the outside - and that just seems like an efficient transfer of energy. That, and I kinda keep expecting some parts to fall off.

Motor is a Turnigy SK3 6374. The shaft is not “keyed”. I’ve cranked down on the pulley set screw. Do I need a different motor, different motor shaft, different pulley, different pulley key?

Grub screw or loctite.

Use a file too make a flat spot where you can put your set screw on & then apply red lock tight all around shaft. Let dry for a whole day. This is what I do & never had an issue for an whole year